A magnetic flux leakage testing is a common nondestructive testing method, which is widely used in a quality testing and a safety monitoring of ferromagnetic material. In recent years, with a continuous improvement and progress of a defect quantification technology, people want to convert a corrosion defect distribution of a pipeline into a form of graphics and images which may be identified directly by naked eyes and further to present the form of graphics and images on a screen in order to achieve the defect visualization.
However, in the related art, defect parameters in three directions may be quantized, but an image corresponding to the defect cannot be generated; or there is a technology to determine which layer of a steel plate the defect is locate, but the technology does not mention the image method of the defect.